'\" t
.TH "SD_BUS_MESSAGE_GET_SIGNATURE" "3" "" "systemd 257~rc3" "sd_bus_message_get_signature"
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.SH "NAME"
sd_bus_message_get_signature, sd_bus_message_is_empty, sd_bus_message_has_signature \- Query bus message signature
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-bus\&.h>
.fi
.ft
.HP \w'const\ char*\ sd_bus_message_get_signature('u
.BI "const char* sd_bus_message_get_signature(sd_bus_message\ *" "message" ", int\ " "complete" ");"
.HP \w'int\ sd_bus_message_is_empty('u
.BI "int sd_bus_message_is_empty(sd_bus_message\ *" "message" ");"
.HP \w'int\ sd_bus_message_has_signature('u
.BI "int sd_bus_message_has_signature(sd_bus_message\ *" "message" ", const\ char\ *" "signature" ");"
.SH "DESCRIPTION"
.PP
\fBsd_bus_message_get_signature()\fR
returns the signature of message
\fImessage\fR\&. If
\fIcomplete\fR
is true, the signature of the whole message is returned, and just the signature of the currently open container otherwise\&.
.PP
\fBsd_bus_message_is_empty()\fR
returns true if the message is empty, i\&.e\&. when its signature is empty\&.
.PP
\fBsd_bus_message_has_signature()\fR
returns true if the signature of the message
\fImessage\fR
matches given
\fIsignature\fR\&. Parameter
\fIsignature\fR
may be
\fBNULL\fR, this is treated the same as an empty string, which is equivalent to calling
\fBsd_bus_message_is_empty()\fR\&.
.SH "RETURN VALUE"
.PP
On success,
\fBsd_bus_message_get_signature()\fR
returns the signature, and
\fBNULL\fR
on error\&.
.PP
The other functions return 0 or a positive integer on success\&. On failure, they return a negative errno\-style error code\&.
.SS "Errors"
.PP
Returned errors may indicate the following problems:
.PP
\fB\-EINVAL\fR
.RS 4
The
\fImessage\fR
parameter is
\fBNULL\fR\&.
.RE
.PP
\fBNULL\fR
.RS 4
The
\fImessage\fR
parameter is
\fBNULL\fR\&.
.RE
.SH "NOTES"
.PP
Functions described here are available as a shared library, which can be compiled against and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.PP
The code described here uses
\fBgetenv\fR(3), which is declared to be not multi\-thread\-safe\&. This means that the code calling the functions described here must not call
\fBsetenv\fR(3)
from a parallel thread\&. It is recommended to only do calls to
\fBsetenv()\fR
from an early phase of the program when no other threads have been started\&.
.SH "HISTORY"
.PP
\fBsd_bus_message_get_signature()\fR,
\fBsd_bus_message_is_empty()\fR, and
\fBsd_bus_message_has_signature()\fR
were added in version 240\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd-bus\fR(3), \fBsd_bus_message_new\fR(3)
